Methods for the analysis of fluids, particularly body fluids, for the presence and quantity of solutes have been known for many years. Recently, an increased desire for the analysis of body fluids for substances, such as steroids and narcotics, has greatly increased the demand for urine analysis. The greater number of samples which need to be tested has created a need for automated analysis procedures which retain at least as much accuracy and reproducibility as conventional methods.
One conventional method of urine analysis comprises contacting a urine specimen with an adsorbent material capable of adsorbing the specific solute in question. For example, a predetermined quantity of adsorbent is placed in a column having openings at both the top and bottom. The adsorbent is held in place by frits, i.e., small plastic screens, which are inert with respect to the materials used in the test procedure. Before introducing the specimen to the test column, the adsorbent is typically cleaned by flushing the column with water or another suitable reagent. The surface of the adsorbent may also be prepared for the specimen by passing one or more reagents through the column. This preparation treatment provides the surface of the adsorbent with a greater affinity for the solute which is being removed from the urine specimen. After the adsorbent has been properly prepared, the specimen is introduced into the column. Since the degree of adsorption of solute by the adsorbent may be highly time-dependent, it is common practice to control the time that the specimen is in contact with the adsorbent by providing a positive pressure at the top of the column or by providing a vacuum at the bottom of the column after the specimen has been introduced into the test column.
Various devices have been disclosed for preparing test samples for analysis. Many of these devices operate in a "batch" manner wherein a number of test samples (a first batch) are placed into a device which performs a first step of a sample preparation procedure on each sample, often one at a time, and then performs a second step on each sample, etc. until the sample preparation procedure has been completed. A laboratory technician then removes the first batch and places a second batch of test samples into the device. Such "batch" devices typically result in a substantial amount of waiting time by laboratory personnel. Furthermore, the "batch" preparation of a large number of test samples using a corresponding number of sample preparation devices, creates the risk of mismatching the collected eluates and test samples.
These disadvantages can be overcome by a method and apparatus for sample preparation which provides the option of processing test samples on a continuous or batch basis.
Known apparatus for preparing and/or analyzing test specimens which operate on a batch basis are typically designed to perform a procedural step on only one of the given specimens at a time, to have the same number of receptacles as specimens in the batch, and to require time consuming modifications for different sized sample preparation devices. Therefore, in order to process a large batch of test specimens in a single run, such apparatus had to be relatively large.
It is, therefore, desirable to provide a smaller, compact sample preparation apparatus which can prepare samples for further analysis on either a batch or continuous basis.
It is also desirable to provide an apparatus which is easily adapted for use with sample preparation devices of different sizes.